This application makes reference to and claims priority and all benefits accruing under 35 U.S.C. Section 119 to an application entitled, xe2x80x9cCall Restriction Method for Base Station in Cellular Radio Communication System,xe2x80x9d filed in the Korean Industrial Property Office on May 3, 1999 and there duly assigned Ser. No. 99-15909.
1. Field of the Invention
The present invention relates generally to a cellular radio communication system, and in particular, to a method for restricting the establishment of an additional reverse call setup or new links established to support hand-offs when the load of the cellular radio communication system exceeds a certain threshold value.
2. Description of the Related Art
A cellular radio communication system divides a whole service area into a plurality of base station areas known as xe2x80x9ccells.xe2x80x9d The base stations are centrally controlled by a mobile switching center (MSC) so that a mobile station (MS) can maintain a call connection while traveling from one cell to another. The cellular radio communication system includes forward channels for transmitting signals from the base stations to the mobile stations, and reverse channels for transmitting signals from the mobile stations to the base stations.
FIG. 1 illustrates the structure of a general base station in a cellular radio communication system. As shown in FIG. 1, the reference numeral 100 denotes a base station. A receiving antenna 110 receives a radio frequency (RF) signal from a mobile station. An RF unit 120 amplifies the received RF signal and filters the amplified RF signal. A frequency down-converter 130 converts the RF signal to an intermediate frequency (IF) signal, and a demodulator 140 demodulates the converted IF signal. A base station control processor (BCP) 150 controls the RF unit 120, the frequency down-converter 130 and the demodulator 140.
The base station 100 allocates a traffic channel for each call in order to exchange voice and data signals. As the traffic channel transmits a voice message corresponding to each call, the output of all traffic channels in the base station is affected by the number of calls being processed by the corresponding base station.
The CDMA (Code Division Multiple Access) cellular radio communication system separates the channels using spreading codes to enhance the capacity. Accordingly, the CDMA base station attempts to serve all new call originations which can sometimes lead to compulsory dropped calls due to the lack of available channels for communication, i.e., hard blocking.
A soft blocking occurs due to the occurrence of an additional call in the system which is a function of cell loading. The loading of a cell corresponds to the ratio between the number of active users and the maximum number of users capable of being serviced within the cell. A call that is additionally set up when the base station has a higher cell loading rate is controlled by the base station control processor 150. Thus, a call which is set up and exceeds the capacity of the base station control processor 150 interferes with all the mobile stations in the service area of the base station 100. In addition, when there are so many calls that can not be supported by the base station 100, the RF unit 120 of the base station 100 becomes inoperable and the call connection during the service is dropped, or the call quality is degraded. Furthermore, the new call origination increase the interference of the mobile stations located in the service area of a given base station 100, thus degrading the quality of the call service provided to the subscribers within the base station 100.
As mentioned above, when the reverse link of the base station has an overload in the cellular radio communication system, the additional call setup increases will increase the interference of the mobile stations, thus degrading the call quality.
It is, therefore, an object of the present invention to provide a method for restricting additional call setups when a base station detects an overload of a reverse link using the noise power level and the receiving power of the base station.
To achieve the above object, there is provided a method for restricting a reverse call in a base station. The method includes the steps of: calculating the noise power of the base station; measuring the total receiving power of the base station; calculating a cell loading factor of the base station using a ratio of the noise power to the total receiving power; comparing the calculated cell loading factor of the base station with a threshold predetermined for call restriction; and, restricting an incoming call to the base station according to the comparison results.